1. Field of the Invention
The invention relates to a method for welding coated sheet metals using a laser hybrid welding process, wherein at least one laser process and one shielding gas welding process are carried out, with a filler material being supplied to the welding site via the shielding gas welding process.
Moreover, the invention relates to a method for starting a laser hybrid welding process for welding coated sheet metals, wherein at least one laser process and one shielding gas welding process are carried out with the laser process preceding the shielding gas welding process, and the shielding gas welding process is positioned in the vicinity of the laser, wherein a filler material is supplied to the welding site via the shielding gas welding process.
Furthermore, the invention relates to a laser hybrid welding torch for welding coated sheet metals or structural components, using a laser or laser optics and at least one shielding gas unit and a wire feeder for a filler material or welding wire.
2. Prior Art
Methods for welding coated sheet metals used, for instance, in the motorcar industry are already known.
DE 101 51 257 A1, for instance, describes a method for connecting clamped and positioned, loose car body parts of a vehicle body in a framing station, in which the body parts are welded by hybrid welding using at least one laser beam and at least one electric arc.
Combined laser electric-arc welding devices, so-called laser hybrid welding units, combine the advantages of a laser, like rapidness and a good heat input into the workpiece, with the advantages of conventional welding methods, e.g. MIG-(metal—inert gas) welding methods, like, for instance, a good gap bridging capacity. US 2001/050273 A1, US 2001/052511 A1, US 2001/047984 A1, US 2003/173343 A1 as well as US 2002/008094 A1, for instance, describe laser hybrid welding methods in which at least one laser process and one shielding gas welding process are carried out. Although it is pointed out that even coated workpieces can be welded together, the problems caused by the evaporation of the coating are not discussed, nor is any solution to overcome those problems suggested.
Basically, it is to be noted in connection with the methods known from the prior art that, in practice, these involve seam preparation operations providing gas evaporation gaps or gas exhalation spaces between the sheet metals in order to enable the escape of the gases forming during welding. Furthermore, weld seam finishing is usually carried out in practice in order to obtain tight weld seams, which means that manual rewelding is performed after the automated welding process in order to close the formed inclusions, craters or holes.